Method for the utilization of waste heat



Aug. 29, 1939. H. A. BRASSERT 2,171,353

METHOD FOR THE UTILIZATION OF WASTE HEAT Filed March 25, 1937 Herman dfiraafier Patented Aug. 29, 1939 UNITED STATES PATENT OFFICE Herman Brassert, Bovington, or to H. A. Brassert & Com

a corporation .0! Illinois Application March 25, 1937, Serial No. 133,019

1 Claim.

This invention relates to a new and improved method for the utilization of waste heat from furnaces and particularly for the utilization of such heat in preheating incoming gas and air to the same or other furnaces.

The invention has particular application in connection with blast furnace gases or other gases of low B. t. u. content, and relates to the use of recuperators for heat transfer.

It is well known in the art to heat the air supply to recuperative furnaces by various methods of recuperation, such as by adjacent brick flues,

, and more'recently, by the use of metal and carborundum tubes. The latter are able to stand 16 very high temperatures and also have high conductivity. These carborundum tubes are used principally where thetemperature is well above 1000" F.,such temperatures precluding the use of steel tubes.

In many steel plants there is a surplus of blast furnace gas which it is desired to use in heating furnaces, for instance, soaking pits. Blast furnace gas has a low thermal value, generally below 100 B. t. us. per cubic foot and high temperature can only be obtained by its use if the gas is preheated as well as the air for combustion. Owing to the danger of leakage through brick work and also the dum by blast furnace gas at high temperatures, these heat transfer mediums have not proved satisfactory. The waste gases from soaking pits and other than continuous heating furnaces are generally in the neighborhood of 2000 F., or much higher than theavailable metal tubes can withstand.

It is an object of the present invention to provide a new and improved method for heat transfer in recuperators and forthe better utilization of waste heat.

It is also an object to a new and improved method of preheating' both air and gas by recuperative means.

It is a further object to provide a. method whereby eflicient heat recovery may be had from high temperature waste gases.

It-is an additional object to provide a method which is simple, which may be adequately controlled and which is adapted for commercial use.

Other and further description proceeds.

objects will appear as the I have shown somewhat diagrammatically in one form of apparathe accompanying drawing, tus which may be used to carry out my improved method.

corrosion of carborun- England, assignpany, Chicago, IlL,

In the drawing:

Figure 1 is a vertical view, partly in section, showing the apparatus, and

Figure 2 is a vertical of Figure 1.

The waste gas oiftake section taken in line 22 5 flue Ii connects with the stack I! in which is located an adjustable damper i3 but the oiftake below the damper ll connects to the stack i2 i3 and communicates with a recuperator l5 containing a plurality of trans- 10 versely extendin per face of the r a flue H.

g refractory tubes l6 which may preferably be form ed of carborundum. The upecuperator i5 discharges into As shown in Figure 1 the left end of the line- 16 I1 communicates with the stack I2 above the damper IS, the communication with the stack being controlled by the damper l8. The right end of the flue I! has intake passage ll roof 2 j of the flue of openings 22 which co cuperator 23 contai The top of the r into the outlet flue to the stack l2 controlled by damper 26.

Figure 2 the gaseous materials to As shownin be heated by the connected thereto an air controlled by damper 20. The so I1 is provided with a plurality mmunicate with a rening a plurality of metal tubes ecuperator 23 discharges 25 which has a connection I recuperator pass transversely through the carborundum tubes i6 and the metal tubes 24. An intake header 2'! is provided on one side of the recuperator l5 and a discharge header 2' cuperator.

upon the opposite side of that re- An intake header 29 is provided upon one side of the recuperator 23 and a discharge header 3| is provided recuperator.

In carrying out of apparatus shown on the opposite side of that my method by using the forms the waste gas, which may be the gases discharged from soaking pits or other heating furnaces the passage i I.

I 3 will be adjust portion of the g heated will also be tor, passing through th 21 to the header 28.

of 2000 F. and the damper 46 passing through this recuperae pipes l6 from the header The waste gas with its temperature considerably reduced, will pass from the recuperator ii to up to the low tem the flue l1 and from that flue 50 perature recuperator 23, The

amount and the temperature of the gases passing be controlled in a adjustment of the through the low temperature recuperator 23 may variety of ways. By suitable dampers l8 and 29, a desired proportion of the gas from recuperator l5 may be returned to the stack l2 and the remainder pass through recuperator 23. Another method of controlling the temperature of the gases passing through recuperator 23 lies in the introduction of low temperature air through passage l9 controlled by damper 20. If desired a. combination of these two methods may be used and it will be apparent that both the quantity of gases passing through the recuperator 23 and the temperature of such gases may be adjusted through a wide range of variations.

It will be understood that the low B. t. u. content of combustible gas will be passing through the metal tubes 24 of the recuperator 23, this gas being introduced through header 29 and taken ofi through header 3!). In carrying out my method I am able to first heat the air to as high a temperature as consistent with the temperature of the waste gases. The temperature of the waste gases may then be reduced to a suitable temperature for passage through the metal recuperator which temperature may be in the range of from 1200 to 1500. If the temperature is not adequately reduced through heat transfer in the lower regenerator, the temperature may be controlled as aforesaid by means of the dampers I8, 20 and 26.

While I have described certain preferred methods of carrying out my invention and shown one form of apparatus suitable for use, it will be understood that the method is capable of change to suit varying conditions and requirements and I contemplate such modifications as come within the spirit and scope of the appended claim.

I claim:

The method of utilizing waste heat in hot gases to preheat blast furnace gas and air by recuperation which comprises transferring heat from the waste gas through refractory walls to air to reduce the gas temperature to a degree non-injurious to metal walls and thereafter reducing the temperature of the gas by the admixture of air, transferring additional heat from the mixture of waste gas and air to the blast furnace gas through impervious metal walls.

HERMAN A. BRASSERT. 

